Surface passivation and hole extraction: Bifunctional interfacial engineering toward high-performance all-inorganic CsPbIBr2 perovskite solar cells with efficiency exceeding 12%

All-inorganic CsPbIBr 2 perovskite solar cells (PSCs) have attracted considerable research attention in recent years due to their excellent thermal stability. However, their power conversion efficiencies (PCEs) are relatively low and still far below the theoretical limit. Here, we report the use of an organic dye molecule (namely VG1-C8) as a bifunctional interlayer between perovskite and the hole-transport layer in CsPbIBr 2 PSCs. Combined experimental and theoretical calculation results disclose that the multiple Lewis base sites in VG1-C8 can effectively passivate the trap states on the perovskite films. Meanwhile, the π-conjugated dye molecule significantly accelerates the hole extraction from the perovskite absorber as evidenced by the photoluminescence analysis. Consequently, the VG1-C8 treatment simultaneously boosts the photovoltage and photocurrent density values from 1.26 V and 10.80 mA cm −2 to 1.31 V and 12.44 mA cm −2 , respectively. This leads to a significant enhancement of PCE from 9.20% to 12.10% under one sun irradiation (AM 1.5G). To our knowledge, this is the record efficiency reported so far for CsPbIBr 2 PSCs. Thus, the present work demonstrates an effective interfacial passivation strategy for the development of highly efficient PSCs.